U.S. patent application number 16/463647 was filed with the patent office on 2020-06-11 for mems scanning module for a light scanner.
The applicant listed for this patent is Blickfeld GmbH. Invention is credited to Florian Petit.
Application Number | 20200183150 16/463647 |
Document ID | / |
Family ID | 60569539 |
Filed Date | 2020-06-11 |
![](/patent/app/20200183150/US20200183150A1-20200611-D00000.png)
![](/patent/app/20200183150/US20200183150A1-20200611-D00001.png)
![](/patent/app/20200183150/US20200183150A1-20200611-D00002.png)
![](/patent/app/20200183150/US20200183150A1-20200611-D00003.png)
![](/patent/app/20200183150/US20200183150A1-20200611-D00004.png)
![](/patent/app/20200183150/US20200183150A1-20200611-D00005.png)
![](/patent/app/20200183150/US20200183150A1-20200611-D00006.png)
![](/patent/app/20200183150/US20200183150A1-20200611-D00007.png)
![](/patent/app/20200183150/US20200183150A1-20200611-D00008.png)
![](/patent/app/20200183150/US20200183150A1-20200611-D00009.png)
![](/patent/app/20200183150/US20200183150A1-20200611-D00010.png)
View All Diagrams
United States Patent
Application |
20200183150 |
Kind Code |
A1 |
Petit; Florian |
June 11, 2020 |
MEMS SCANNING MODULE FOR A LIGHT SCANNER
Abstract
A scanning module (100) for a light scanner (99) comprises a
base (141) and an interface element (142) which is configured to
secure a mirror surface (151). The scanning module (100) also
comprises at least one support element (101, 102) which extends
between the base (141) and the interface element (142) and has an
extension perpendicular to the mirror surface (151) which is no
less than 0.7 mm. The base (141), the interface element (142) and
the at least one support element (101) are integrally formed.
Inventors: |
Petit; Florian; (Muenchen,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Blickfeld GmbH |
Muenchen |
|
DE |
|
|
Family ID: |
60569539 |
Appl. No.: |
16/463647 |
Filed: |
November 22, 2017 |
PCT Filed: |
November 22, 2017 |
PCT NO: |
PCT/DE2017/101007 |
371 Date: |
May 23, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01S 17/003 20130101;
F16C 11/12 20130101; G01S 7/4817 20130101; B81B 2201/04 20130101;
G02B 26/105 20130101; B81B 3/0021 20130101; G02B 26/0858
20130101 |
International
Class: |
G02B 26/08 20060101
G02B026/08; G01S 7/481 20060101 G01S007/481; B81B 3/00 20060101
B81B003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 23, 2016 |
DE |
10 2016 014 001.1 |
Claims
1. A scanning module for a light scanner, which comprises: a base,
an interface element which is configured to secure a mirror
surface, and at least one support element, which is configured to
be resilient, and extends between the base and the interface
element and has an extension perpendicular to the mirror surface
which is no less than 0.7 mm, wherein the base, the interface
element and the at least one support element are integrally
formed.
2. The scanning module according to claim 1, wherein the at least
one support element is configured to be rod-shaped along a
longitudinal axis which has a component perpendicular to the mirror
surface, wherein the length of the at least one support element is
no less than 2 mm.
3. The scanning module according to claim 1, wherein a longitudinal
axis of the at least one support element encloses an angle with a
surface normal of the mirror surface, which is in the range of
-60.degree. to +60.degree..
4. The scanning module according to claim 1, wherein the at least
one support element comprises at least two support elements, and
wherein longitudinal axes of the at least two support elements
pairwise in each case enclose angles with one another which are no
greater than 45.degree., wherein the at least two support elements
are arranged in a plane.
5. (canceled)
6. The scanning module according to claim 1, which moreover
comprises: an additional base which is connected to the base and is
not integrally formed therewith, an additional interface element,
which is connected to the interface element, not integrally formed
therewith and configured to secure the mirror surface, and at least
one additional support element which is configured to be resilient,
and extends between the additional base and the additional
interface element.
7. The scanning module according to claim 6, wherein the at least
one support element is reproduced by reflection at a plane of
symmetry on the at least one additional support element.
8. The scanning module according to claim 6, wherein the base is
connected to the additional base via a base spacer, and/or wherein
the at least one interface element is connected to the at least one
additional interface element via an interface spacer.
9. (canceled)
10. The scanning module according to claim 1, wherein the base
comprises a central region and an edge region, wherein the at least
one support element extends away from the central region, and
wherein the edge region has a form-induced resilience which is
greater than the form-induced resilience of the central region.
11. The scanning module according to claim 10, wherein the edge
region has a recess.
12. (canceled)
13. The scanning module according to claim 1, which moreover
comprises: the mirror surface which is connected to the interface
element and which is not integrally formed therewith, a mirror with
the mirror surface and a back side opposite the mirror surface,
wherein the interface element is attached to the back side of the
mirror, and wherein the at least one support element extends away
from a back side of the mirror, which is opposite the mirror
surface.
14. (canceled)
15. The scanning module according to claim 1, wherein the at least
one support element comprises at least two support elements, and
wherein a distance between two adjacent support elements of the at
least two support elements is in the range of 2%-50% of the length
of at least one of the at least two support elements.
16. (canceled)
17. The scanning module according to claim 1, wherein the at least
one support element comprises n support elements, wherein n is
greater than or equal to two, and wherein the n support elements
are arranged with n-fold rotational symmetry.
18. (canceled)
19. (canceled)
20. A light scanner which comprises: the scanning module
comprising: a base, an interface element which is configured to
secure a mirror surface, and at least one support element, which is
configured to be resilient, and extends between the base and the
interface element and has an extension perpendicular to the mirror
surface which is no less than 0.7 mm, wherein the base, the
interface element and the at least one support element are
integrally formed, at least one actuator which is configured to
excite a torsion mode of the at least one support element or a
transverse mode of the at least one support element, wherein the at
least one actuator is configured to excite the torsion mode by
tilting of the base, and wherein the at least one actuator is
attached on an edge region of the base.
21. (canceled)
22. (canceled)
23. The light scanner according to claim 20, wherein the at least
one actuator comprises a first piezo bending actuator and a second
piezo bending actuator, and wherein the base extends between the
first bending piezo actuator and the second bending piezo
actuator.
24. A method which comprises: defining an etching mask by means of
lithography on a wafer, etching the wafer by means of the etching
mask in order to obtain at least one etched structure which forms a
scanning module, and securing a mirror with mirror surface on at
least one interface element of the scanning module.
25. (canceled)
26. The method according to claim 24, which moreover comprises:
connecting multiple etched structures which form the scanning
module before securing the mirror.
27. The method according to claim 26, wherein each of the multiple
etched structures comprises a base, an interface element (142,
142-1, 142-2), and at least one support element which extends
between the respective base and the respective interface element,
wherein the connection of the multiple etched structures occurs on
the bases and on the interface elements of the multiple etched
structures.
28. The method according to claim 26, wherein the connection of the
multiple etched structures comprises at least one of the following
techniques: gluing, anodic bonding, direct bonding, eutectic
bonding, thermocompression bonding, and adhesive bonding.
29. The method according to claim 26, wherein the connection of the
multiple etched structures occurs via spacers.
30. (canceled)
31. A scanning module for a resonant light scanner, which
comprises: a mirror with a mirror surface and with a back side
opposite the mirror surface, and at least one resilient support
element which extends away from the back side and which is produced
by means of micro-electro mechanical system (MEMS) techniques.
Description
TECHNICAL FIELD
[0001] The invention relates in general to a scanning module for a
light scanner. In particular, the invention relates to a scanning
module with at least one resilient support element which extends
between a base and an interface element for securing a mirror
surface and has an extension perpendicular to the mirror surface
which is no less than 0.7 mm. This enables resonant scanning.
BACKGROUND
[0002] The distance measurement of objects is desirable in various
technology fields. For example, in the context of autonomous
driving applications, it can be desirable to detect objects in the
surroundings of vehicles and, in particular, to determine a
distance to the objects.
[0003] One technique for distance measurement of objects is the
so-called LIDAR technology (light detection and ranging; sometimes
also LADAR). Here, pulsed laser light is emitted by an emitter. The
objects in the surroundings reflect the laser light. These
reflections can subsequently be measured. By determining the
propagation time of the laser light, a distance to the objects can
be determined.
[0004] For the spatially resolved detection of the objects in the
surroundings, it is possible to scan the laser light. Depending on
the radiation angle of the laser light, different objects in the
surroundings can thereby be detected.
[0005] Microelectromechanical (MEMS) components can be used for
this purpose, in order to implement a laser scanner. See, for
example, DE 10 2013 223 937 A1. Here, typically, a mirror is
connected via lateral spring elements to a substrate. The mirror
and the spring elements are integrally formed or integrated with
the substrate. The mirror is released by appropriate etching
processes from a wafer.
[0006] However, such techniques have certain disadvantages and
limitations. For example, the scanning angle is often relatively
limited, for example, on the order of magnitude of
20.degree.-60.degree.. In addition, the usable mirror area is often
limited; typical mirrors can have a side length of 1 mm-3 mm.
Therefore, in LIDAR techniques, the detector aperture can be
limited; this has the result that only relatively close objects can
be reliably measured.
[0007] In order to remedy these disadvantages, it is known to
operate multiple mirrors in a synchronized manner. See, for
example, Sandner, Thilo, et al. "Large aperture MEMS scanner module
for 3D distance measurement." MOEMS-MEMS. International Society for
Optics and Photonics, 2010. However, the synchronization can be
relatively elaborate. In addition, it can then be impossible or
only limitedly possible to implement two-dimensional scanning. Here
too, the scanning angle is limited.
BRIEF SUMMARY OF THE INVENTION
[0008] Therefore, there is a need for improved techniques for
measuring distances of objects in the surroundings of a device. In
particular, there is a need for such techniques which remedy at
least some of the above-mentioned limitations and
disadvantages.
[0009] This aim is achieved by the features of the independent
claim. The dependent claims define embodiments.
[0010] In an example, a scanning module for a light scanner
comprises a base and an interface element. The interface element is
configured to secure a mirror surface. The scanning module also
comprises at least one resilient support element which extends
between the base and the interface element and which has an
extension perpendicular to the mirror surface which is no less than
0.7 mm. The base, the interface element and the at least one
support element are integrally formed.
[0011] Since the at least one support element is designed to be
resilient, it can also be referred to as a spring element. Thereby,
at least one degree of freedom of motion of the at least one
support element can be excited in a resonant manner. This
corresponds to the resonant operation of the light scanner
(resonant scanner). This is to distinguish it from non-resonant
light scanners, for example, with ball bearings for a constant
rotating motion or step motors.
[0012] For example, it would be possible that at least one support
element has an extension perpendicular to the base which is no less
than 1 mm, optionally no less than 3.5 mm, moreover optionally no
less than 7 mm.
[0013] Since the at least one support element has a significant
extension perpendicularly to the mirror surface, this element--in
contrast to the lateral spring elements in the prior art--can also
be referred to as a perpendicularly oriented support element. By
means of such an arrangement, particularly large scanning angles
can be generated, for example, in the range of
120.degree.-180.degree..
[0014] In some examples, it would be possible for the scanning
module to have at least two support elements. The scanning module
could comprise at least three support elements, optionally at least
four support elements. Thereby, particularly robust scanning
modules having a low susceptibility to vibrations can be
produced.
[0015] For example, it would be possible that the longitudinal axes
of the at least two support elements pairwise in each case enclose
angles which are no greater than 45.degree., optionally no greater
than 10.degree., moreover optionally no greater than 1.degree..
This means that the at least two support elements can be arranged
parallel or substantially parallel to one another.
[0016] The at least two support elements could have an arrangement
with rotational symmetry with respect to a central axis. Here, it
would be possible for the rotation symmetry to be n-fold, wherein n
refers to the number of the at least two support elements. Thereby,
it is possible to avoid non-linear effects during resonant
operation of the light scanner.
[0017] For the resonant operation of the light scanner, at least
one degree of freedom of motion of the at least one support element
can be excited.
[0018] The at least one degree of freedom of motion could comprise
a transverse mode and a torsion mode, wherein the natural frequency
of the lowest transverse mode is greater than the natural frequency
of the lowest torsion mode.
[0019] The at least one degree of freedom of motion could comprise
a transverse mode and a torsion mode, wherein the lowest transverse
mode is degenerated with the lowest torsion mode. Thereby, it can
be achieved that the scanning module is particularly robust with
respect to external excitations.
[0020] The torsion mode can correspond to a twisting of the two
support elements. The torsion mode can denote a twisting of each
individual support element along the corresponding longitudinal
axis. Optionally, the torsion mode can also denote a twisting of
multiple support elements into one another.
[0021] It would be also possible that the distance between two
adjacent support elements of the at least two support elements is
in the range of 2%-50% of the length of at least one of the at
least two support elements, optionally in the range of 10%-40%,
moreover optionally in the range of 12-20%. This can enable a
compact design and an adapted frequency of the torsion mode.
[0022] It would be possible that the at least two support elements
have lengths which differ from one another by no more than 10%,
optionally no more than 2%, moreover optionally no more than
0.1%.
[0023] For example, it would be possible for the scanning module to
have a balancing weight. The balancing weight can be attached to at
least one of the at least one interface element. The balancing
weight can in particular be integrally formed with the at least one
interface element. For example, it would be possible for the
balancing weight to be implemented by a change of the
cross-sectional area along the longitudinal axis of the at least
one interface element. By means of the balancing weight, the moment
of inertia can be changed. Thereby, the frequency of the torsion
mode of the at least one interface element can be adapted to the
frequency of the transverse modes of the at least one interface
element. Depending on the design of the balancing weight, it would
be possible, for example, that a degeneration of the natural
frequencies of the orthogonal transverse modes of the at least one
interface element is eliminated.
[0024] In an example, the scanning module comprises a first piezo
bending actuator, a second piezo bending actuator, and the base
which is arranged between the first piezo bending actuator and the
second piezo bending actuator. The piezo bending actuators could
thus excite at least one support element via the base in a coupled
manner.
[0025] Here, the first piezo bending actuator could have an
elongate form along a first longitudinal axis, and the second piezo
bending actuator could have an elongate form along a second
longitudinal axis. The first longitudinal axis and the second
longitudinal axis could enclose an angle with one another which is
less than 20.degree., optionally smaller than 10.degree., moreover
optionally smaller than 1.degree..
[0026] The first longitudinal axis and/or the second longitudinal
axis could enclose an angle with a longitudinal axis of the at
least one support element, which is less than 20.degree.,
optionally less than 10.degree., moreover optionally less than
1.degree.. Alternatively, it would also be possible that the first
longitudinal axis and/or the second longitudinal axis enclose an
angle with a longitudinal axis of the at least one support element,
which is in the range of 90.degree..+-.20.degree., optionally in
the range of 90.degree..+-.10.degree., moreover optionally in the
range of 90.degree..+-.1.degree.. The base could have a
longitudinal extension along a first longitudinal axis of the first
bending piezo actuator, which is in the range of 2-20% of the
length of the first piezo bending actuator along the first
longitudinal axis, optionally in the range of 5-15%. In this
manner, particularly large scanning angles can be achieved, and an
efficient excitation of different degrees of freedom of motion of
the at least one support element can be achieved.
[0027] The base could have a longitudinal extension along a second
longitudinal axis of the second bending piezo actuator, which is in
the range of 2-20% of the length of the second piezo bending
actuator along the second longitudinal axis, optionally in the
range of 5-15%. Thereby, it can be achieved that the bending piezo
actuator can apply a sufficiently strong force onto the base for
the efficient excitation of different degrees of freedom of motion
of the at least one support element.
[0028] The first piezo bending actuator could have an elongate form
along a first longitudinal axis. The second piezo bending actuator
could also have an elongate form along a second longitudinal axis.
The first piezo bending actuator could extend along the first
longitudinal axis, and the second piezo bending actuator could
extend along the second longitudinal axis along a longitudinal axis
of the at least one support element to a freely mobile end of the
at least one support element.
[0029] The device could also comprise a driver which is configured
to control the first bending piezo actuator with a first signal
form and to control the second bending piezo actuator with a second
signal form. Here, the first signal form and the second signal form
could have out-of-phase signal contributions.
[0030] Optionally, it would also be possible for the second signal
form to have additional in-phase signal contributions which are
optionally amplitude modulated. For example, the amplitude of the
in-phase signal contributions for the time duration required for
the scanning of the scanning area (correlates with the refresh
rate), could increase or decrease monotonically. A linear time
dependence of the envelope curve would be possible.
[0031] Here, the signal contributions could have a first frequency,
wherein the additional signal contributions have a second
frequency, wherein the first frequency is in the range of 95-105%
of the second frequency or in the range of 45-55% of the second
frequency.
[0032] It would be possible for the first signal form and/or the
second signal form to have a DC portion.
[0033] A method comprises defining an etching mask by means of
lithography on a wafer. The method also comprises etching the wafer
by means of the etching mask for obtaining at least one etched
structure which forms a scanning module. The method moreover
comprises securing a mirror with mirror surface on an interface
element of the scanning module.
[0034] The method can be used for producing a scanning module
according to various examples described herein. Since the scanning
module is produced from a wafer--for example, a silicon wafer or a
silicon on insulator wafer (SOI wafer), such techniques can also be
referred to as MEMS techniques.
[0035] The securing of the mirror on the interface element can
comprise at least one of the following techniques: gluing, anodic
bonding, direct bonding, eutectic bonding, thermocompression
bonding, adhesive bonding.
[0036] For example, as adhesive, an epoxy resin or a polymethyl
methacrylate (PMMA) could be used.
[0037] The method could moreover comprise connecting several etched
structures which form the scanning module before securing the
mirror. Corresponding techniques can be used for connecting the
etched structures which were described above in the context of
securing the mirror, i.e., gluing, anodic bonding, direct bonding,
eutectic bonding, thermocompression bonding, adhesive bonding.
[0038] In general, a large number of structures can be defined for
each wafer, so that a large number of scanning modules can be
obtained for each wafer. Parallel wafer-level processing can thus
avoid individual handling of individual scanning modules. At a
certain stage in the processing, the release of individual
structures can occur, for example, by cutting or sawing the wafer.
Scanning module-level processing can then occur. In general, it
would be possible for the connection of the multiple etched
structures forming the scanning module to occur at the wafer
level--i.e., before releasing individual scanning modules. However,
it would also be possible for the connection of the multiple etched
structures to occur at the scanning module level--i.e., after
releasing individual scanning modules.
[0039] Each of the multiple etched structures can comprise a base,
an interface element, and at least one support element which
extends between the respective base and the respective interface
element. Then, the connection of the multiple etched structures to
the bases and to the interface elements of the multiple etched
structures can occur.
[0040] The connection can occur directly or via spacers.
[0041] A scanning module for a resonant light scanner comprises a
mirror. The mirror has a mirror surface. The mirror also has a back
side. The back side is located opposite the mirror surface. The
scanning module also has at least one resilient support element
which extends away from the back side. The at least one resilient
support element is produced by MEMS techniques.
[0042] This can mean that the at least one resilient support
element is manufactured by wafer etching and lithography from a
silicon or SOI wafer. This can mean, for example, that the at least
one resilient support element is formed from a monocrystalline
material and can thus withstand particularly strong tensions.
[0043] The features explained above and features described below
can be used not only in the corresponding explicitly represented
combinations but also in other combinations or alone, without
leaving the scope of protection of the present invention.
BRIEF DESCRIPTION OF THE FIGURES
[0044] FIG. 1A diagrammatically illustrates a scanning module for a
light scanner according to various examples, wherein the scanning
module in the example of FIG. 1A has two support elements arranged
parallel to one another, and a mirror which is not integrally
formed.
[0045] FIG. 1B diagrammatically illustrates a scanning module for a
light scanner according to various examples, wherein the scanning
module in the example of FIG. 1B has two support elements arranged
parallel to one another, and a mirror which is integrally
formed.
[0046] FIG. 1C diagrammatically illustrates a scanning module for a
light scanner according to various examples, wherein the scanning
module in the example of FIG. 1C has two support elements arranged
parallel to one another, and a mirror surface which is applied on
an interface element of the scanning module.
[0047] FIG. 2 diagrammatically illustrates a scanning module for a
light scanner according to various examples, wherein the scanning
module has two support elements arranged parallel to one another,
and a mirror not integrally formed and which can be tilted with
respect to the longitudinal axis of the support elements.
[0048] FIG. 3 is a diagrammatic perspective view of a scanning
module according to various examples, which has a base, an
interface element and two support elements extending between the
base and the interface element.
[0049] FIG. 4 is a diagrammatic perspective view of a scanning
module according to various examples, which has a base, an
interface element and two support elements extending between the
base and the interface element, wherein the base has two edge
regions which are configured to be connected to piezo
actuators.
[0050] FIG. 5A is a diagrammatic view onto a scanning module
according to various examples, wherein the base is connected to two
piezo bending actuators.
[0051] FIG. 5B is a diagrammatic view onto a scanning module
according to various examples, wherein the base is connected to two
piezo bending actuators.
[0052] FIG. 6A is a diagrammatic side view of piezo bending
actuators according to various examples.
[0053] FIG. 6B is a diagrammatic view onto a scanning module
according to various examples, wherein the base is connected to two
piezo bending actuators.
[0054] FIG. 7 diagrammatically illustrates a light scanner
according to various examples.
[0055] FIG. 8 diagrammatically illustrates out-of-phase signal
forms which can be used for operating piezo bending actuators
according to various examples.
[0056] FIG. 9 diagrammatically illustrates in-phase signal forms
which can be used for operating piezo bending actuators according
to various examples.
[0057] FIG. 10 diagrammatically illustrates out-of-phase signal
forms with DC portion, which can be used for operating piezo
bending actuators according to various examples.
[0058] FIG. 11 diagrammatically illustrates in-phase signal forms
with DC portion, which can be used for operating piezo bending
actuators according to various examples.
[0059] FIG. 12 diagrammatically illustrates an amplitude modulation
of in-phase signal forms as a function of time according to various
examples.
[0060] FIG. 13 diagrammatically illustrates a superposition figure
for two degrees of freedom of motion of at least one support
element and a scanning region defined by the superposition figure
according to various examples.
[0061] FIG. 14 illustrates a spectrum of the excitation of at least
one support element, wherein FIG. 14 represents a degeneration
between a torsion mode and a transverse mode according to various
examples.
[0062] FIG. 15 illustrates a spectrum of the excitation of at least
one support element, wherein FIG. 15 represents in an eliminated
degeneration between a torsion mode and a transverse mode according
to various examples.
[0063] FIG. 16 diagrammatically illustrates a scanning module for a
light scanner according to various examples, wherein the scanning
module in the example of FIG. 15 has two support elements arranged
parallel to one another with respective balancing weight.
[0064] FIG. 17 is a perspective view of a scanning module for a
light scanner according to various examples, wherein the scanning
module has two pairs of support elements in different planes.
[0065] FIG. 18 diagrammatically illustrates a torsion mode for the
scanning module according to the example of FIG. 17.
[0066] FIGS. 19 and 20 diagrammatically illustrate a transverse
mode of a scanning module with a separate support element according
to various examples.
[0067] FIGS. 21 and 22 diagrammatically illustrate a transverse
mode of a scanning module with two parallel support elements
according to various examples.
[0068] FIG. 23 diagrammatically illustrates a scanning module for a
light scanner according to various examples, wherein the scanning
module in FIG. 23 has two support elements arranged parallel to one
another with respective piezo material.
[0069] FIG. 24 is a flow chart of an example of a method for
producing a scanning module.
[0070] FIG. 25 diagrammatically illustrates the production of a
scanning module according to various examples.
[0071] FIG. 26 is a cross-sectional view of the scanning module
according to FIG. 25.
DETAILED DESCRIPTION OF EMBODIMENTS
[0072] The above-described characteristics, features and advantages
of this invention and the manner in which they are achieved are
clarified and can be better understood based on the following
description of the embodiment examples which are explained in
further detail in reference to the drawings.
[0073] Below, the present invention is explained in further detail
based on preferred embodiments in reference to the drawings. In the
figures, identical reference numerals denote identical or similar
elements. The figures are diagrammatic representations of different
embodiments of the invention. Elements represented in the figures
are not necessarily represented true to scale. Instead, the
different elements represented in the figures are reproduced in
such a manner that their function and general purpose are
understandable to the person skilled in the art. Connections and
couplings between functional units and elements represented in the
figures can also be implemented as indirect connection or coupling.
Functional units can be implemented as hardware, software or as a
combination of hardware and software.
[0074] Below, various techniques for scanning light are described.
The techniques described below can enable, for example, the
two-dimensional scanning of light. The scanning can denote repeated
emission of the light at different radiation angles. For this
purpose, the light can be deflected by a deflecting unit. The
scanning can refer to the repeated scanning of different points in
the surroundings by means of the light. For example, the number of
different points in the surroundings and/or the number of different
radiation angles can establish a scanning region.
[0075] In various examples, the scanning of light can occur by the
temporal superposition and optionally by a spatial superposition of
two resonantly driven motions in accordance with different degrees
of freedom of at least one mobile support element. Thereby, in
various examples, a superposition figure can be traced. Sometimes,
the superposition figure is also referred to as a Lissajous figure.
The superposition figure can describe a sequence with which
different radiation angles are implemented by the motion of the
support element.
[0076] In various examples, it is possible to scan laser light.
Here, for example, coherent or incoherent laser light can be used.
It would be possible to use polarized or unpolarized laser light.
For example, it would be possible to use the laser light in a
pulsed manner. For example, short laser pulses having pulse widths
in the range of femtoseconds or picoseconds or nanoseconds can be
used. For example, a pulse duration can be in the range of 0.5-3
nanoseconds. The laser light can have a wavelength in the range of
700-1800 nm. For the sake of simplicity, reference is made below
primarily to laser light; however, the various examples described
herein can also be used for the scanning of light from other light
sources, for example, broad-band light sources or RGB light
sources. RGB light sources here denote in general light sources in
the visible spectrum, wherein the color space is covered by
superposition of several different colors--for example, red, green,
blue or cyan, magenta, yellow, black.
[0077] In various examples, at least one support element having a
form- or material-induced resilience is used for the scanning of
the light. Therefore, the at least one support element could also
be referred to as a spring element. Then, at least one degree of
freedom of motion of the at least one support element can be
excited, for example, a torsion mode and/or a transverse mode.
I.e., a resonant excitation of the corresponding modes occurs.
Thereby, a mirror which is connected to a mobile end of the at
least one support element can be moved. Therefore, the mobile end
of the at least one support element defines an interface element.
Thereby, light can be scanned. For example, it would be possible to
use more than one single support element, for example, two or three
or four support elements. These support elements can optionally be
arranged symmetrically with respect to one another.
[0078] For example, the mobile end could be moved in one or two
dimensions. For this purpose, one or more actuators can be used.
For example, it would be possible for the mobile end to be tilted
with respect to a fastening means of the at least one support
element; this results in a curvature of the at least one support
element. This can correspond to a first degree of freedom of
motion; this degree of freedom can be referred to as transverse
mode (or also sometimes as wiggle mode). Alternatively or
additionally, it would be possible to twist the mobile end along a
longitudinal axis of the support element (torsion mode). This can
correspond to a second degree of freedom of motion. By the motion
of the mobile end, it is possible to achieve that laser light is
emitted at different angles. For this purpose a deflecting unit
such as a mirror, for example, can be provided. Thereby,
surroundings can be scanned with the laser light. Depending on the
extent of the motion of the mobile end, scanning regions of
different size can be implemented.
[0079] In the various examples described here, it is possible in
each case to excite the torsion mode alternatively or additionally
to the transverse mode, i.e., a temporal and spatial superposition
of the torsion mode and the transverse mode would be possible.
However, this temporal and spatial superposition can also be
eliminated. In other examples, other degrees of freedom of motion
could also be implemented.
[0080] For example, the deflecting unit can be implemented as a
prism or a mirror. For example, the mirror could be implemented by
a wafer, for example, a silicon wafer, or a glass substrate. For
example, the mirror could have a thickness in the range of 0.05
.mu.m-0.1 mm. For example, the mirror could have a thickness of 25
.mu.m or 50 .mu.m. For example, the mirror could have a thickness
in the range of 25 .mu.m to 75 .mu.m. For example, the mirror could
be designed to be square, rectangular or circular. For example, the
mirror could have a diameter of 3 mm to 12 mm or of 8 mm in
particular.
[0081] In general, such techniques for scanning light can be used
in a wide variety of application fields. Examples include
endoscopes and RGB projectors and printers. In various examples,
LIDAR techniques can be used. The LIDAR techniques can be used to
carry out a spatially resolved distance measurement of objects in
the surroundings. For example, the LIDAR technique can include
measurements of the propagation time of the laser light between the
mirror, the object and a detector. In general, such techniques for
the scanning of light can be used in a wide variety of application
fields. Examples include endoscopes, and RGB projectors and
printers. In various examples, LIDAR techniques can be used. The
LIDAR techniques can be used to carry out a spatially resolved
distance measurement of objects in the surroundings. For example,
the LIDAR technique can include measurements of the propagation
time of the laser light.
[0082] Various examples are based on the finding that it can be
desirable to carry out the scanning of the laser light with high
accuracy with regard to the radiation angle. For example, in the
context of LIDAR techniques, a spatial resolution of the distance
measurement can be limited by an inaccuracy of the radiation angle.
Typically, a higher (lower) spatial resolution is achieved, the
more (less) accurately the radiation angle of the laser light can
be determined.
[0083] Below, techniques are described for providing a particularly
robust laser scanner. In various examples, this is achieved in that
scanning module is provided which comprises a support element.
Here, the support element is integrally formed with a base and with
an interface element configured to secure the mirror surface.
[0084] Due to the integrally formed design, it is possible to
achieve that a particularly strong flux of force can be transferred
via the base to the support element. Thereby, one or more degrees
of freedom of motion of the support element can be excited
particularly efficiently. Thereby, it can be achieved in turn that
the support element performs a motion with a particularly large
amplitude. Thereby, large scanning angles can be implemented. In
addition, it is avoided that for example an adhesive or another
connection means--which would have to be used in the non-integrally
formed design--tears or yields, thereby damaging the scanning
module.
[0085] In order to integrally form the different parts of the
scanning module, MEMS techniques can be used. For example, the
scanning module could be produced by etching techniques from a
wafer. The wafer can have a thickness of, for example, 500 .mu.m.
For example, techniques of wet chemical etching or dry etching
could be used, for example, reactive ion etching (RIE), for
example, dry RIE (DRIE). The wafer can be a silicon wafer or a
silicon on insulator (SOI) wafer, for example. The insulator could
be arranged approximately 100 .mu.m under a surface of the wafer.
Here, the insulator can act, for example, as an etching stop. Here
it is possible to use front-side etching and/or back-side etching
in order to release the different parts of the scanning module. For
example, it would be possible to define etching masks on the wafer
by means of lithography. In this manner, in particular, the
different parts of the scanning module can be designed to form a
single piece/integrally formed and optionally even to be
monocrystalline.
[0086] Below, techniques are also described for providing a laser
scanner which can implement particularly large scanning angles.
This is achieved in various examples in that the support element
has an extension perpendicular to the mirror surface which is no
less than 0.7 mm. In comparison to conventional MEMS-based
micromirrors, the support element therefore does not extend only in
the plane of the mirror surface, but also has a significant
extension perpendicular to the mirror surface. For example, the
support element could be designed to be rod shaped along a
longitudinal axis, wherein the longitudinal axis has a component
perpendicular to the mirror surface. Here, the support element
could have local changes of the cross-sectional area, in order to
implement a balancing weight.
[0087] By means of such techniques, it is possible to achieve that
the mirror surface can move particularly freely. Thereby, large
amplitudes of motion can be achieved, whereby in turn large
scanning angles are made possible.
[0088] FIG. 1A illustrates aspects with regard to a scanning module
100. The scanning module 100 comprises a base 141, two support
elements 101, 102 and an interface element 142. Here, the base 141,
the support elements 101, 102 and the interface element 142 are
integrally formed. The support elements 101, 102 are designed in
one plane (plane of the drawing of FIG. 1A). In the example of FIG.
1A, the support elements 101, 102 are designed to be straight,
i.e., in the resting state they have no curvature or bend. In the
various examples described herein, a corresponding straight,
rod-shaped configuration of support elements can be used.
[0089] For example, it would be possible that the base 141, the
support elements 101, 102 and the interface element 142 are
obtained by means of MEMS processes by etching a silicon wafer (or
another semiconductor substrate). In such a case, the base 141, the
support elements 101, 102 and the interface element 142 can be
designed in particular to be monocrystalline.
[0090] It would be possible that the distance between two adjacent
support elements 101, 102 is in the range of 2%-50% of the length
211 of at least one of the at least two support elements,
optionally in the range of 10%-40%, moreover optionally in the
range of 12-20%. It would be possible that the at least two support
elements have lengths 211 which do differ from one another by no
more than 10%, optionally by no more than 2%, moreover optionally
by no more than 0.1%. Thereby, a particularly large amplitude of
corresponding degrees of freedom of motion can be achieved. For
example, it would be possible that the longitudinal axes 111, 112
of the support elements 101, 102 in each case pairwise enclose
angles with one another which are no greater than 45.degree.,
optionally no greater than 10.degree., moreover optionally no
greater than 1.degree.. The support elements 101, 102 have an
arrangement with rotational symmetry with respect to a central axis
220. In the example of FIG. 1A, this is a two-fold rotational
symmetry.
[0091] It would also be possible for the scanning module 100 to
have only a single support element or more than two support
elements.
[0092] FIG. 1A also illustrates aspects with regard to a laser
scanner 99. The laser scanner 99 comprises the scanning module 100
and a mirror 150. In the example of FIG. 1A, the mirror 150, which
forms on the front side a mirror surface 151 with high reflectivity
(for example, more than 95% at a wavelength of 950 .mu.m,
optionally >99%, moreover optionally >99.999%; for example,
aluminum or gold in a thickness of 80-250 nm) of light 180, is not
integrally formed with the base 141, the support elements 101, 102
and the interface element 142. For example, the mirror 150 could be
glued to the interface element 142. The interface element 142 can
in fact be configured to secure the mirror surface 151. For this
purpose, for example, the interface element 142 could have a
contact surface which is configured to secure a corresponding
contact surface of the mirror 150. In order to connect the mirror
150 to the interface element 142, it would be possible to use, for
example, one or more of the following techniques: gluing,
soldering.
[0093] Between the interface element 142 and the mirror surface
151, a back side 152 of the mirror 150 is arranged. The interface
element 142 is arranged on the back side 152 of the mirror 150.
From FIG. 1 it can be seen that the support elements extend away
from the back side 152 of the mirror 150 to the base 141. Thereby,
space-intensive, frame-like structures as in conventional MEMS
attachments can be avoided. The mirror 150 can thus be connected
via the interface element 142 to the support elements 101, 102.
Thereby, a two-piece production is possible, so that no complicated
integrated back side structuring as in conventional MEMS
attachments has to occur.
[0094] By means of such techniques, large mirror surfaces can be
implemented, for example, no less than 10 mm{circumflex over ( )}2,
optionally no less than 15 mm{circumflex over ( )}2. Thereby, in
the context of LIDAR techniques which use the mirror surface 151
also as detector aperture, a high accuracy and range can be
achieved.
[0095] In the example of FIG. 1A, the support elements 101, 102
have an extension perpendicular to the mirror surface 151; this
extension could be, for example, approximately 2-8 mm, in the
example of FIG. 1A. The support elements are designed to be in
particular rod-shaped along corresponding longitudinal axes 111,
112. In FIG. 1A, the surface normal 155 of the mirror surface 151
is represented; the longitudinal axes 111, 112 are oriented
parallel to the surface normal 155, i.e., they enclose an angle of
0.degree. with said surface normal.
[0096] Therefore, the extension of the support elements 101, 102
perpendicular to the mirror surface 151 is equal to the length 211
of the support elements 101, 102. In general, it would be possible
for the length 211 of the support elements 101, 102 to be no
shorter than 2 mm, optionally no shorter than 4 mm, moreover
optionally no shorter than 6 mm. For example, it would be possible
for the length of the support elements 101, 102 to be no greater
than 20 mm, optionally no greater than 12 mm, moreover optionally
no greater than 7 mm. When multiple support elements are used, they
can all have the same length.
[0097] Depending on the relative orientation of the longitudinal
axes 111, 112 with respect to the mirror surface 151, it would also
be possible for the extension of the support elements 101, 102
perpendicular to the mirror surface 151 to be shorter than the
length 211 thereof (since only the projection parallel to the
surface normal 155 is taken into consideration). In general, it
would be possible that for extension of the support elements 101,
102 perpendicular to the mirror surface 151 to be no less than 0.7
mm. Such a value is greater than the typical thickness of a wafer
from which the scanning module 100 can be produced. Thereby,
particularly large scanning angles for the light 180 can be
implemented.
[0098] The support elements 101, 102 could have, for example, a
rectangular cross section. The support elements 101, 102 could also
have a square cross section. However, other cross-sectional shapes,
such as, for example, circular, triangular, etc., would also be
possible. Typical side lengths of the cross section of the support
elements 101, 102 can be in the range of 50 .mu.m to 200 .mu.m,
optionally they can be approximately 100 .mu.m. The short side of
the cross section in general could be no less than 50% of the long
side of the cross section; this means that the support elements
101, 102 may be designed not as flat elements. In this manner, it
is ensured that the material in the region of the support elements
101, 102 can absorb sufficiently strong tensions without being
damaged. However, at the same time, the form-induced resilience of
the material in the region of the support elements 101, 102 can
assume sufficiently high values to enable a motion of the interface
142 elements with respect to the base 141.
[0099] For example, a torsion mode and/or a transverse mode of the
support elements 101, 102 could be used in order to move the
interface element 142--and thus the mirror 150. Thereby, the
scanning of light can be implemented (in FIG. 1A, the resting state
of the support elements 101, 102 is represented).
[0100] In the example of FIG. 1A, the scanning module 102 comprises
support elements 101, 102 which are arranged in one plane (the
plane of the drawing of FIG. 1A). By using two support elements
101, 102, the scanning module 100 can be implemented with
particularly high robustness. In particular, thereby, the tension
for each support element 101, 102 can be reduced. On the other
hand, in the case of a single support element, it can be possible
to particularly satisfactorily enable two-dimensional scanning of
the light 180.
[0101] FIG. 1B illustrates aspects with regard to a scanning module
100. The scanning module 100 comprises a base 141, two support
elements 101, 102 and an interface element 142. Here, the base 141,
the support elements 101, 102 and the interface element 142 are
integrally formed.
[0102] The example of FIG. 1B here basically corresponds to the
example of FIG. 1A. However, in the example of FIG. 1B, the mirror
150 is integrally formedwith the interface element 142 or the
support elements 101, 102 and the base 141. In order to achieve the
largest possible mirror surface 151, in the example of FIG. 1B, a
projection beyond a central region of the interface element 142 is
provided. Thereby, it can be achieved that the flux of force
between the scanning module 100 and the mirror 150 does not have to
be transferred via an adhesive.
[0103] FIG. 1C illustrates aspects with regard to a scanning module
100. The scanning module 100 comprises a base 141, two support
elements 101, 102 and an interface element 142. Here, the base 141,
the support elements 101, 102 and the interface element 142 are
integrally formed.
[0104] The example of FIG. 1C here basically corresponds to the
example of FIG. 1B. In the example of FIG. 1C, the mirror 150 and
the interface element 142 are implemented by one and the same
element. The mirror surface 151 is directly attached to the
interface element 142. This enables a particularly simple
design.
[0105] FIG. 2 illustrates aspects with regard to a scanning module
100. The scanning module 100 comprises a base 141, two support
elements 101, 102 and an interface element 142. Here the base 141,
the support elements 101, 102 and the interface element 142 are
integrally formed.
[0106] The example of FIG. 2 here basically corresponds to the
example of FIG. 1A. However, in the example of FIG. 2, the
longitudinal axes 111, 112 of the support elements 101, 102 are not
oriented perpendicularly to the mirror surface 151. In FIG. 2, the
angle 159 between the surface normal 155 of the mirror surface 151
and the longitudinal axes 111, 112 is represented. In the example
of FIG. 2, the angle 159 is 45.degree., but in general it could be
in the range of -60.degree. to +60.degree., or optionally in the
range of -45.degree..+-.15.degree. or in the range of
+45.degree..+-.15.degree., i.e., substantially 45.degree..
[0107] In particular, in FIG. 2, a scenario is represented, in
which one beam path of the light 180 extends parallel to the
longitudinal axes 111-112 of the support elements 101, 102, and an
additional beam path of the light 180--after or before deflection
by the mirror surface 151 extends perpendicularly to the
longitudinal axes 111-112. In general, the beam path of the light
180 can extend parallel to the central axis 220
[0108] Such a tilting of the mirror surface 151 with respect to the
longitudinal axes 111, 112 can be particularly advantageous when
the torsion mode of the support elements 101, 102 is used for
moving the mirror 150. Then, a periscope-like scanning of the light
180 can be implemented.
[0109] The periscope-like scanning by means of the torsion mode has
the advantage that--to the extent that the mirror 150 is also used
as detector aperture--the size of the detector aperture is not
dependent on the scanning angle; the angle between incident light
and mirror 150 is in fact not dependent on the scanning angle. This
is different from reference implementations, in which, due to
tilting of the mirror, the size of the detector aperture--and thus
the sensitivity of the measurement--varies as a function of the
scanning angle.
[0110] FIG. 3 illustrates aspects with regard to a scanning module
100. The scanning module 100 comprises a base 141, two support
elements 101, 102 and an interface element 142. Here, the base 141,
the support elements 101, 102 and the interface element 142 are
integrally formed. FIG. 3 is a perspective view of the scanning
module 100.
[0111] In particular, in FIG. 3, the drawing shows how a direction
1901 of the front-side etching and a direction 1902 of the
back-side etching are oriented. For example, the scanning module
100 could be produced by appropriate two-step etching of an SOI
wafer along the directions 1901, 1902. The boundary surfaces
between insulator and silicon could define the support elements
101, 102.
[0112] For example, here, the wafer surface could be oriented
perpendicularly to the directions 1901, 1902. It follows from a
comparison of FIGS. 1A, 1B, 1C, 2 with FIG. 3 that the mirror
surface 151 is not oriented perpendicularly to the wafer surface.
Thereby, particularly large lengths 211 of the at least one support
element 101, 102 can be made possible. This in turn enables large
scanning angles.
[0113] In the example of FIG. 3, the thickness 1998 of the base 141
and of the interface element 142 is different from the thickness
1999 of the support elements 101, 102. In other examples, it would
be possible for the base 141, the interface element 142 and the
support elements 101, 102 to have the same thickness. This is with
respect to the thicknesses 1998, 1999 in etching direction of the
MEMS structuring, i.e., perpendicularly to a wafer normal with
regard to the front-side structuring and back-side structuring in
directions 1901, 1902. The wafer normal typically correlates with a
certain crystal direction.
[0114] FIG. 4 illustrates aspects with regard to a scanning module
100. The scanning module 100 comprises a base 141, two support
elements 101, 102 and an interface element 142. Here, the base 141,
the support elements 101, 102 and the interface element 142 are
integrally formed. FIG. 4 is a perspective view of the scanning
module 100.
[0115] The example of FIG. 4 basically corresponds to the example
of FIG. 3. In the example of FIG. 4, the base 141 comprises a
central region 145 and two edge regions 146 arranged on different
sides of the central region 145. The support elements 101, 102 are
connected to the central region 145. The central region 145 and the
edge regions 146 are all integrally formed.
[0116] In the example of FIG. 3, the edge regions 146 have a
substantially smaller thickness than the central region 145. For
example, the thickness of the edge regions 146 could be no greater
than 30% of the thickness of the central region 145. Due to the
reduced thickness of the edge regions 146, it can be achieved that
they have a greater form-induced resilience than the central region
145. In general, other measures could also be taken in order to
achieve that the edge regions 146 have a greater form-induced
resilience than the central region 145. For example, recesses or
grooves could be provided, which provide the resilience.
[0117] The edge regions 146 can be used to establish a connection
with piezo actuators. The central region 145 here establishes the
connection with the support elements 101, 102.
[0118] FIG. 5A illustrates aspects with regard to a laser scanner
99. The laser scanner 99 comprises the scanning module 100 which,
for example, could be configured according to the various other
examples described herein (however, in FIG. 5A, a scanning module
100 having only a single support element 101 is represented as an
example).
[0119] FIG. 5A illustrates in particular aspects with regard to
piezo actuators 310, 320. In various examples, piezo bending
actuators 310, 320 can be used for the excitation of the support
element 101.
[0120] For example, in general, a first and a second piezo bending
actuator can be used. It would be possible for the first piezo
bending actuator and/or the second piezo bending actuator to be of
plate-shaped design. In general, a thickness of the piezo bending
actuators can be, for example, in the range of 200 .mu.m-1 mm,
optionally in the range of 300 .mu.m-700 .mu.m. For example, it
would be possible that the first piezo bending actuator and/or the
second piezo bending actuator has/have a layer structure which
comprises an alternating arrangement of multiple piezoelectric
materials. Said piezo bending actuators can have a piezoelectric
effect of different strength. Thereby, a bending can be brought
about, similar to that of a bimetallic strip during temperature
changes. For example, it is possible that the first piezo bending
actuator and/or the second piezo bending actuator is/are secured at
a securing site: an end opposite the securing site can then be
moved as a result of a bending or curving of the first piezo
bending actuator and/or of the second piezo bending actuator.
[0121] By using piezo bending actuators, a particularly efficient
and strong excitation can be achieved. The piezo bending actuators
in fact can move the base 141 and, in particular--for the
excitation of a torsion mode of the at least one support
element--tilt said base. In addition, it can be possible to achieve
a high integration of the device for the excitation. This can mean
that the necessary installation space can be dimensioned to be
particularly small.
[0122] In particular, in the example of FIG. 5A, the piezo
actuators 310, 320 are designed as piezo bending actuators. This
means that the application of a tension to electrical contacts of
the piezo bending actuators 310, 320 brings about a curving or
bending of the piezo bending actuators 310, 320 along the
longitudinal axes 319, 329 thereof. For this purpose, the piezo
bending actuators 310, 320 have a layer structure (not represented
in FIG. 5A and oriented perpendicularly to the plane of the
drawing). In this manner, an end 315, 325 of the piezo bending
actuators 310, 320 is deflected with respect to a securing site
311, 321 perpendicularly to the respective longitudinal axis 319,
329 (in the example of FIG. 5A, the deflection is oriented
perpendicularly to the plane of the drawing). The deflection 399 of
the piezo bending actuators 310, 320 as a result of the bending is
represented in FIG. 6A.
[0123] FIG. 6A in a side view of the piezo bending actuators 310,
320. FIG. 6A shows the piezo bending actuators 310, 320 in a
resting position, for example, without driver signal or
tension/curvature.
[0124] Again with regard to FIG. 5A: For example, the securing site
in 311, 321 could establish a rigid connection between the piezo
bending actuators 310, 320 and a housing of the laser scanner 99
(not represented in FIG. 5A).
[0125] The base 141 could have a longitudinal extension of the
longitudinal axes 319, 329, which is in the range of 2-20% of the
length of the piezo bending actuators 310, 320 along the
longitudinal axes 319, 329, optionally in the range of 5-15%.
Thereby, a sufficiently strong excitation can be achieved; the base
141 then damps the motion of the piezo bending actuators 310, 320
only relatively weakly.
[0126] In the example of FIG. 5A, the piezo bending actuators 310,
320 are arranged substantially parallel to one another. Tilting of
the longitudinal axes 319, 329 with respect to one another would
also be possible, in particular as long as the tilting occurs in
one plane.
[0127] From the example of FIG. 5A, it can be seen that the
connection of the piezo bending actuators 310, 320 with the support
element 101 is implemented via the edge regions 146 of the base
141. Since these edge regions 146 have resilience, the bending 399
can be absorbed and leads to a deflection of the base 141. Thereby,
one or more degrees of freedom of motion of the interface element
101 can be excited in a coupled manner via the base 141. Thereby, a
particularly efficient and space-saving excitation is achieved.
[0128] In the example of FIG. 5A, the piezo bending actuators 310,
320 extend away from the interface element 142. However, it would
also be possible for the piezo bending actuators 310, 320 to extend
along at least 50% of the length thereof toward the interface
element 142. Thereby, a particularly compact arrangement can be
achieved. This is shown in FIG. 5B.
[0129] FIG. 5B illustrates aspects with regard to a laser scanner
99. The laser scanner 99 comprises the scanning module 100 which
could be configured for example according to the various other
examples described herein (however, in FIG. 5B, a scanning module
100 with only a single support element 101 is represented).
[0130] The example of FIG. 5B here basically corresponds to the
example of FIG. 5A. However, here the piezo bending actuators 310,
320 extend toward the interface element 142 or toward a freely
mobile end of the at least one support element 101. Thereby, a
particularly compact structure of the light scanner 99 can be
achieved.
[0131] It follows from a comparison of FIGS. 5A, 5B, 6A with FIG. 4
that, in the case of excitation via the edge regions 146, a coupled
excitation of the multiple support elements 101, 102 occurs. For
example, it can be achieved that a piezo bending actuator excites
all the support elements 101, 102 together via a flux of force led
through the base 141. Correspondingly, this could be achieved in
that the flux of force is applied to a magnetic material connected
to all the support elements 101, 102 by means of a common magnetic
field of a magnetic field coil. Such techniques of coupled
excitation have the advantage that an energy efficient and
space-saving excitation is enabled. In addition, due to the
coupling, it can be prevented that different actuators have to be
operated with phase coherence, which simplifies the implementation.
Due to the coupled excitation, in particular a coupled torsion mode
and/or a coupled transverse mode can be excited.
[0132] The actuator can be configured for the direct force action
for exciting the degree of freedom of motion, i.e., the use of a
parametric excitation--as is the case, for example, in reference
implementations with electrostatic interdigital finger
structures--can be avoided.
[0133] While, in the examples of FIGS. 5A, 5B and 6A, the
longitudinal axes 319, 329 are oriented parallel to the
longitudinal axis of the support element 101, it would also be
possible in other examples for the longitudinal axes 319, 329 of
the piezo bending actuators to be arranged perpendicularly to the
longitudinal axis of the support element 101. This is represented
in FIG. 6B. In general, the longitudinal axes 319, 329 could
enclose an angle of 90.degree..+-.20.degree. with the longitudinal
axis of the at least one support element, optionally of
90.degree..+-.5.degree., moreover optionally of
90.degree..+-.1.degree.
[0134] FIG. 7 illustrates aspects with regard to a laser scanner
99. The laser scanner 99 comprises a control unit 4001 which could
be implemented, for example, as a microprocessor or application
specific integrated circuit (ASIC). The control unit 4001 could
also be implemented as a field programmable array (FPGA). The
control unit 4001 is configured to output control signals to a
driver 4002. For example, the control signals could be output in
digital or analog form.
[0135] The driver 4002 in turn is configured to generate one or
more voltage signals and to output said voltage signals at
corresponding electrical contacts of the piezo actuators 310, 320.
Typical amplitudes of the voltage signals are in the range of 50 V
to 250 V.
[0136] The piezo actuators 310, 320 in turn are coupled to the
scanning module 100, as described above with regard to FIGS. 5 and
6, for example. Thereby, one or more degrees of freedom of motion
of the scanning module 100, in particular of one or more support
elements 101, 102 of the scanning module 100, can be excited.
Thereby, the mirror surface 151 is deflected. Thereby, the
surrounding region of the laser scanner 99 can be scanned with
light 180.
[0137] FIG. 8 illustrates aspects with regard to signal forms 800
which can be used in order to control the piezo actuators 310, 320
according to various examples described herein. For example, the
signal forms 800 can be output by the driver 4002. FIG. 8 plots in
particular the amplitude of the signal forms 800 as a function of
time.
[0138] In the example of FIG. 8, a signal contribution 811 (solid
line) is represented, which is used to control the piezo bending
actuators 310. In addition, in the example of FIG. 8, a signal
contribution 821 (dashed line) is represented, which is used to
control the piezo bending actuators 320. From the example of FIG.
8, it can be seen that the signal contributions 811, 821 are
configured to be out-of-phase. In the example of FIG. 8, this means
that the signal contributions 811, 821 have the same frequency as
well as a phase shift of 180.degree..
[0139] Thereby, it can be achieved that the bending piezo bending
actuators 310 are curved or moved upward (curved or moved
downward), while the piezo bending actuators 320 are curved or
moved downward (curved or moved upward). Thereby, it can be
achieved in turn that the base 141 is tilted alternatingly to the
left and to the right (with respect to a central axis 220 of one or
more support elements 101, 102). Therefore, with such a
configuration of the signal forms 800, a particularly efficient
excitation of the torsion mode of the support element or of the
support elements 101, 102 can be achieved.
[0140] FIG. 9 illustrates aspects with regard to signal forms 800,
which can be used to control the piezo bending actuators 310, 320
according to various examples described herein. FIG. 9 plots in
particular the amplitude of the signal forms 800 as a function of
time.
[0141] In the example of FIG. 9, a signal contribution 812 (solid
line) is represented, which is used to control the piezo bending
actuators 310. In addition, in the example of FIG. 9, a signal
contribution 822 (dashed line) is represented, which is used to
control the piezo bending actuators 320. From the example of FIG.
9, it can be seen that the signal contributions 812, 822 are
configured to be in-phase. In the example of FIG. 9, this means
that the signal contributions 812, 822 have the same frequency and
a phase shift of 0.degree.. In some examples, it would be possible
for the in-phase signal contributions 812, 822 to have an amplitude
modulation.
[0142] Due to the in-phase signal contributions 812, 822, it can be
achieved that the piezo bending actuators 310 are curved or moved
upward (curved or moved downward), while the piezo bending
actuators 320 are curved or moved upward (curved or moved
downward). As a result, it can in turn be achieved that the base
141 is moved alternatingly upward and downward (with respect to the
central axis 220). Therefore, by means of such a configuration of
the signal forms 800, a particularly efficient excitation of
transverse modes of the support element or of the support elements
101, 102 can occur.
[0143] In some examples, it would be possible for the signal
contributions 811, 821 to be applied temporally superposed with the
signal contributions in 812, 822. This can be desirable in
particular if only a single support element is used. Then, a
temporal and spatial superposition of a torsion mode and a
transverse mode of the at least one support element can be
obtained. Thereby it can be achieved that a two-dimensional
scanning region is scanned, wherein the light is deflected at the
single mirror surface. This can achieve a particularly space-saving
integration of the laser scanner 99.
[0144] In other examples, it would also be possible for either the
out-of-phase signal contributions 811, 821 or else the in-phase
signal contributions 812, 822 to be applied. This can be
particularly desirable if more than a single support element is
used. Then, either the torsion mode or the transverse mode of the
at least one support element can be excited. Thereby, by deflection
at the mirror surface, a one-dimensional scanning region can be
scanned. In order to nevertheless scan a two-dimensional scanning
region, it would be possible, for example, that two laser scanners
sequentially deflect the light; here, the two laser scanners can be
operated in a synchronized manner.
[0145] However, below, reference is made primarily to scenarios in
which a temporal or //and// spatial superposition of different
degrees of freedom of motion of the at least one support element is
used to scan a two-dimensional scanning region.
[0146] A typical frequency of the signal contributions 811, 812,
821, 822 is, for example, in the range of 50 Hz to 1.5 kHz,
optionally in the range of 200 Hz to 1 kHz, moreover optionally in
the range of 500 Hz to 700 Hz. In this manner, appropriate scanning
frequencies can be achieved.
[0147] In the examples of FIGS. 8 and 9, scenarios are illustrated
in which, for the excitation of the piezo bending actuators 310,
320, the out-of-phase signal contributions 811, 821 have
approximately the same frequency as the in-phase signal
contributions 812, 822. In general, it would be possible that for
the out-of-phase signal contributions 811, 821 to have a first
frequency in the range of 95-105% of a second frequency of the
in-phase signal contributions 812, 822. By means of such an
implementation of the frequencies of the signal forms 800, it can
be achieved that a particularly efficient superposition figure of
the different degrees of freedom of motion of the at least one
support element 101, 102 can be achieved.
[0148] In particular, it can be achieved that a high refresh rate
can be achieved, without certain regions of the scanning region
being scanned multiple times by nodes in the superposition figure.
In particular, such implementations of the frequencies of the
signal forms 800 can exploit the fact that a degeneration of the
different excited degrees of freedom of motion of the at least one
support element 101, 102 in the frequency space is present. For
example, it is possible that a degeneration of the frequency of the
torsion mode of the at least one support element 101, 102 and of
the frequency of the transverse mode of the at least one support
element 101, 102 can be achieved by an appropriate configuration of
one or more of the following parameters: length 211 of the at least
one support element 101, 102; moment of inertia of the at least one
support element 101, 102 and/or a balancing weight which is
attached to the at least one support element 101, 102, and moment
of inertia of the interface element 142 and/or of the mirror
150.
[0149] However, in other examples, it would be possible for the
out-of-phase signal contributions 811, 821 to have a first
frequency other than the second frequency of the in-phase signal
contributions 812, 822. For example, the first frequency of the
out-of-phase signal contributions 811, 821 could be in the range of
45-55% of the second frequency of the in-phase signal contributions
812, 822, i.e., approximately half of the second frequency. In
other examples, the first frequency could also be double the second
frequency and assume an entirely different value. By such an
elimination of the degeneration between the different degrees of
freedom of motion of the at least one support element 101, 102,
which are excited by the out-of-phase signal contributions 811, 821
and in-phase signal contributions 812, 822, non-linear interactions
between the corresponding degrees of freedom of motion can be
avoided. For example, the formation of a parametric oscillator by
the transverse modes and/or the torsion mode can be avoided.
Thereby, a particularly targeted excitation of the at least one
support element 101, 102 can be achieved.
[0150] Due to the superposition of the in-phase signal
contributions 811, 821 with the out-of-phase signal contributions
812, 822, it can be achieved that the signal forms 800 on the piezo
bending actuators 810 have a certain phase shift with respect to
the signal forms 800 on the piezo bending actuators 820. This phase
shift can be varied, for example, as a function of the relative
amplitude of the in-phase signal contributions 811, 821 and the
out-of-phase signal contributions 812, 822 with respect to one
another. In other words, the actual signal forms 800 can be
decomposed into the in-phase signal contributions 811, 821 and the
out-of-phase signal contributions 812, 822. In some examples, a
driver used for generating the signal forms 800 can already
generate the superposition of the in-phase signal contributions
811, 821 with the out-of-phase signal contributions 812, 822.
[0151] FIG. 10 illustrates aspects with regard to signal forms 800
which can be used to control the piezo bending actuators 310, 320
according to various examples described herein. FIG. 10 plots in
particular the amplitude of the signal forms 800 as a function of
time.
[0152] The example of FIG. 10 basically corresponds to the example
of FIG. 8. However, in the example of FIG. 10, the signal
contributions 811, 821 have a respective DC portion 801. In some
examples, it would also be possible that only one of the signal
contributions 811, 821 has a DC portion 801 (horizontal dashed line
in FIG. 10). In some examples, it would also be possible for the
two signal contributions 811, 821 to have differently dimensioned
DC portions 801, for example, in terms of magnitude and/or
sign.
[0153] Due to the provision of the DC portion 801, it can be
achieved that a bias of the at least one support element 101,
102--i.e., a DC deflection of the at least one support element 101,
102 is achieved. Thereby, for example, an offset of the at least
one support element and/or specifications for the field of view of
the corresponding scanner can be compensated or taken into
consideration.
[0154] FIG. 11 illustrates aspects with regard to signal forms 800
which can be used to control the piezo bending actuators 310, 320
according to various examples described herein. FIG. 11 plots in
particular the amplitude of the signal forms 200 as a function of
time.
[0155] The example of FIG. 11 basically corresponds to the example
of FIG. 9. However, in the example of FIG. 11, the signal
contributions 812, 822 have a respective DC portion 801. In
general, it is possible that only some of the signal contributions
812, 822 have a DC portion 801. Different signal contributions can
also have different DC portions.
[0156] FIG. 12 illustrates aspects with regard to an amplitude
modulation of the signal contributions 812, 822. In particular,
FIG. 12 illustrates the amplitude of the signal contributions 812,
822 as a function of time.
[0157] In the example of FIG. 12, the time duration 860 is
represented, which is necessary for scanning a superposition
figure. This means that the time duration 860 can correspond to a
refresh rate of the laser scanner 99.
[0158] From FIG. 12, it can be seen that the amplitude of the
in-phase signal contributions 812, 822 increases monotonically and
continuously as a function of time during the time duration 860.
However, the amplitude could also increase stepwise. The amplitude
could also decrease monotonically.
[0159] FIG. 12 also illustrates aspects with regard to an amplitude
modulation of the signal contributions 811, 821. From FIG. 12, it
can be seen that the amplitude of the out-of-phase signal
contributions 811, 821 does not vary.
[0160] By such techniques, a particularly efficient scanning of the
laser light can be implemented. In particular, it can be possible
that a superposition figure is obtained which has no nodes or at
least only few nodes. Thereby, a large scanning region can be
scanned with a high refresh rate.
[0161] It has been observed that particularly good results can be
achieved if a continuous amplitude modulation without jumps is
selected. Particularly good results can be achieved in particular
in the case of a sine- or cosine-shaped amplitude modulation. Then
in particular, non-linear effects are suppressed particularly
satisfactorily. A particularly well defined superposition figure
can be obtained.
[0162] FIG. 13 illustrates aspects with regard to a superposition
FIG. 900. FIG. 13 illustrates in particular aspects with regard to
a scanning region 915 (dashed line in FIG. 13) which is defined by
the superposition FIG. 900. FIG. 13 here shows the scanning angle
901 which can be achieved by a first degree of freedom of motion
501 of the at least one support element 101, 102. FIG. 13 also
shows the scanning angle 902 which can be achieved by a second
degree of freedom of motion 502 of the at least one support element
101, 102 (the scanning angles are also indicated in FIG. 1, for
example).
[0163] For example, it would be possible for the first degree of
freedom of motion 501 to correspond to a transverse mode of the at
least one support element 101, 102. Then, it would be possible for
the transverse mode 501 to be excited by the in-phase signal
contributions 812, 822. Correspondingly, it would be possible for
the degree of freedom of motion 902 to correspond to a torsion mode
of the at least one support element 101, 102. Then, it would be
possible that the torsion mode 502 is excited by the out-of-phase
signal contributions 811, 821.
[0164] The superposition FIG. 900 according to the example of FIG.
13 is obtained if the transverse mode 501 and the torsion mode 902
have the same frequency. In addition, the superposition FIG. 900
according to the example of FIG. 13 is then obtained if the
amplitude of the transverse mode 501 is increased by the amplitude
modulation of the in-phase signal contributions 812, 822 (compare
FIG. 12) during the time duration 860. Thereby, it is in fact
achieved that the superposition FIG. 900 in the form of an "opening
eye" is obtained, i.e., with increasing amplitude of the transverse
mode 501 greater scanning angles 901 are obtained (represented by
the vertical dotted arrows in FIG. 13). Thereby, scanning lines can
be obtained (horizontal dotted arrows in FIG. 13), by means of
which the surroundings of the laser scanner 99 can be scanned. By
repeated emission of light pulses, different image points 951 can
then be obtained. Superposition figures with multiple nodes are
avoided, whereby a particularly high refresh rate can be achieved.
In addition, it is avoided that certain regions between the nodes
are not scanned.
[0165] FIG. 14 illustrates aspects with regard to resonance curves
1301, 1302 of the degrees of freedom of motion 501, 502 which, for
example, can implement the superposition FIG. 900 according to the
example of FIG. 13. FIG. 14 here illustrates the amplitude of the
excitation of the respective degree of freedom of motion 501, 502.
A resonance spectrum according to the example of FIG. 14 can be
particularly desirable, if a temporal and spatial superposition of
the different degrees of freedom of motion 501, 502 of the at least
one support element 101, 102 is desired for the two-dimensional
scanning.
[0166] The resonance curve 1301 of the transverse mode 501 has a
maximum 1311 (solid line). In FIG. 14, the resonance curve 1302 of
the torsion mode 502 is also represented (dashed line). The
resonance curve 1302 has a maximum 1312.
[0167] The maximum 1312 of the torsion mode 502 is at a lower
frequency than the maximum 1311 of the transverse mode, which could
be the transverse mode 501 of lowest order, for example. The
torsion mode 502 can thus form the fundamental mode of the system.
Thereby, it can be achieved that the scanning module is
particularly robust with respect to external interfering influences
such as vibrations, etc. This is the case, since such external
excitations typically excite the transverse mode 501 particularly
efficiently, while, on the other hand, not exciting the torsion
mode 502 particularly efficiently.
[0168] For example, the resonance curves 1301, 1302 could be of
Lorentzian form. This would be the case if the corresponding
degrees of freedom of motion 501, 502 can be described by a
harmonic oscillator.
[0169] The maxima 1311, 1312 are shifted with respect to one
another in terms of frequency. For example, the frequency spacing
between the maxima 1311, 1312 could be in the range of 5 Hz to 20
Hz.
[0170] In FIG. 14, the full widths at half maximum 1321, 1322 of
the resonance curves 1301, 1302 are also represented. Typically,
the full width at half maximum is defined by the damping of the
corresponding degree of freedom of motion 501, 502. In the example
of FIG. 14, the full widths at half maximum 1321, 1322 are
identical; however, in general, the full widths at half maximum
1321, 1322 could be different from one another. In some examples,
different techniques can be used in order to increase the full
widths at half maximum 1321, 1322. For example, a corresponding
adhesive could be provided, of which certain sites are arranged,
for example, between the piezo bending actuators 310, 320 and the
base 141.
[0171] In the example of FIG. 14, the resonance curves 1301, 1302
have an overlap region 1330 (represented shaded). This means that
the transverse mode 501 and the torsion mode 502 are degenerated.
In the overlap region 1330, both the resonance curve 1301 and the
resonance curve 1302 have significant amplitudes. For example, it
would be possible for the amplitudes of the resonance curves 1301,
1302 in the overlap region to be in each case no less than 10% of
the corresponding amplitudes at the respective maximum 1311, 1312,
optionally in each case not <5%, moreover optionally in each
case not <1%. By means of the overlap region 1330, it can be
achieved that the two degrees of freedom of motion 501, 502 can be
excited in a coupled manner, namely in each case in a semi-resonant
manner at a frequency 1399. The frequency 1399 is between the two
maxima 1311, 1312. Thereby, the temporal and spatial superposition
can be achieved. However, on the other hand, nonlinear effects can
be suppressed or avoided by coupling between the two degrees of
freedom of motion 501, 502.
[0172] FIG. 15 illustrates aspects with regard to resonance curves
1301, 1302 of the degrees of freedom of motion 501, 502. In the
example of FIG. 15, the two degrees of freedom of motion 501, 502
have no overlap regions. There is an eliminated degeneration.
Therefore, when the excitation frequency 1399 is used, only the
torsion mode 502 is excited. This can be desirable if the scanning
module is to implement only one-dimensional scanning. This can be
desirable particularly when more than one support element is
used.
[0173] For example, the degree of freedom of motion 502 can
correspond to a torsion mode. The torsion mode 502 can form a
fundamental mode of the kinematic system, i.e., it is possible that
no additional degrees of freedom of motion with smaller natural
frequencies are present.
[0174] Due to the semi-resonant excitation to the sides of the
maximum 1312, non-linear effects can be prevented.
[0175] For adjusting or shifting the resonance curves 1301, 1302,
one or more balancing weights can be provided, which, for example,
can be integrally formedwith the at least one support element 101,
102. A corresponding example is represented in FIG. 16.
[0176] The example of FIG. 16 basically corresponds to the example
of FIG. 1. However, in the example of FIG. 16, balancing weights
1371, 1372 are provided on the support elements 101, 102. The
balancing weights 1371, 1372 are integrally formedwith the support
elements 101, 102. Due to the balancing weights 1371, 1372, the
frequency of the torsion mode 502 can be changed. The balancing
weights 1371, 1372 correspond to a local enlargement of the cross
section of the rod-shaped support elements 101, 102.
[0177] FIG. 17 illustrates aspects with regard to a laser scanner
99. In the example of FIG. 17, a scanning module 100 is
represented, which comprises a first pair of support elements
101-1, 102-1 and a second pair of support elements 102-1, 102-2.
The first pair of support elements 101-1, 102-1 is arranged in a
plane; the second pair of support elements 101-1, 102-2 is also
arranged in a plane. These planes are arranged parallel to one
another and offset with respect to one another.
[0178] Each pair of support elements is here associated with a
corresponding base 141-1, 141-2 and a corresponding interface
element 142-1, 142-2. The two interface elements 142-1, 142-2 here
establish a connection with a mirror 150. In this manner, it can be
achieved that a particularly stable scanning module 100 is
provided, which has a large number of support elements. In
particular, the scanning module 100 can comprise support elements
which are arranged in different planes. This can enable a
particularly high robustness.
[0179] From FIG. 17, it can also be seen that the base 141-1 is not
integrally formed with the base 141-2. In addition, the interface
element 142-1 is not integrally formed with the interface element
142-2. The support elements 101-1, 102-1 are not designed to form a
single with the support elements 102-1, 102-2. In particular, it
would be possible that the different above-mentioned parts are
produced from different regions of a wafer and are subsequently
connected to one another by gluing or anodic bonding, for example.
Other examples for connection techniques comprise: fusion bonding,
fusion or direct bonding, eutectic bonding, thermocompression
bonding, and adhesive bonding. Corresponding connection surfaces
160 are marked in FIG. 17. By means of such techniques, it is
possible to achieve that the scanning module 100 can be produced
particularly simply. In particular, it is not necessary that the
complete scanning module 100 is produced in the form of a single
piece or integrally from a wafer. Instead, the scanning module 100
can be generated in a two-step production process. At the same time
however, this cannot significantly lower the robustness; due to the
large-area connection surfaces 160, a particularly stable
connection between the base 141-1 and of the base 141-2 and
respectively between the interface element 142-1 and the interface
element 142-2 can be produced.
[0180] In the example of FIG. 17, the base 141-1 is directly
connected to the base 141-2; in addition, the interface element
142-1 is directly connected to the interface element 142-2. This is
made possible by the thickness variation in comparison to the
support elements 101-1, 101-2, 102-1, 102-2 (compare FIG. 3). In
other examples, the base 141-1, the base 141-2, the interface
element 142-1, the interface element 142-2 and the support elements
101-1, 101-2, 102-1, 102-2 can all have the same thickness; then,
connection via spacers could occur (not shown in FIG. 17).
[0181] In the scenario of FIG. 17, it is possible for the base
141-1, the support elements 101-1, 102-1, and the interface element
142-1 to be reproduced by mirroring at a plane of symmetry (in
which the connection surfaces 160 are also located) onto the base
141-2, the support elements 102-1, 102-2 and the interface element
142-2. Thereby, a highly symmetric structure can be achieved. In
particular, a rotationally symmetric structure can be achieved. The
rotational symmetry can have an order n=4; i.e., equal to the
number of support elements 101-1, 101-2, 102-1, 102-2 used. Such a
symmetric structure with respect to the central axis 220 can in
particular have advantages with regard to the excitation of the
torsion mode 502. Non-linearities can be avoided.
[0182] FIG. 18 illustrates aspects with regard to the torsion mode
502. FIG. 18 diagrammatically illustrates the deflection of the
torsion mode 502 for the scanning module 100 according to the
example of FIG. 17 (in FIG. 18, the deflected state is represented
with solid lines and the resting state is represented with dashed
lines).
[0183] In FIG. 18, the rotation axis 220 of the torsion mode 502 is
represented. The rotation axis 220 lies in the plane of symmetry
221 which reproduces the base 141-1 onto the base 141-2 or the
support elements 101-1, 101-2 onto the support elements 102-1,
102-2.
[0184] The multiple support elements 101-1, 101-2, 102-1, 102-2
thus are twisted (I) both into one another along the central axis
220; and also (II) in each case individually along the longitudinal
axes thereof. Therefore, the torsion mode 502 can also be referred
to as coupled torsion mode 502 of the support elements 101-1,
101-2, 102-1, 102-2. This is promoted by the geometric arrangement
of the support elements 101-1, 101-2, 102-1, 102-2 with respect to
one another, namely in particular by the parallel arrangement of
the support elements 101-1, 101-2, 102-1, 102-2 with respect to one
another--that is to say with a particularly small distance between
the support elements 101-1, 101-2, 102-1, 102-2 in comparison to
the length thereof. This coupled torsion mode 502 can be referred
to as parallel kinematics of the support elements 101-1, 101-2,
102-1, 102-2.
[0185] In the example of FIG. 18, the support elements 101-1,
102-1, 101-2, 102-2 are arranged rotationally symmetrically with
respect to a central axis 220. In particular, a four-fold
rotational symmetry is present. The presence of a rotational
symmetry means, for example, that the system of the support
elements 101-1, 102-1, 101-2, 102-2 can be brought into
superposition with itself by rotation. The order of the rotational
symmetry denotes how often per 360.degree. rotation angle the
system of the support elements 101-1, 102-1, 101-2, 102-2 can be
brought into superposition with itself. In general, the rotational
symmetry could be n-fold, where n denotes the number of support
elements used.
[0186] Due to the rotationally symmetric arrangement of high order,
the following effect can be achieved: In the case of excitation of
the torsion mode 502, nonlinearities can be reduced or suppressed.
The plausibility of this can be shown by the following example: for
example, the support elements 101-1, 102-1, 101-2, 102-2 could be
arranged in such a manner that the longitudinal axes and the
central axis 220 all lie in one plane. The rotational symmetry
would then be two-fold (and not four-fold as in the example of FIG.
18). In such a case, the orthogonal transverse modes 501 (different
directions perpendicular to the central axis 220) have different
frequencies--due to different moments of inertia. Thus, for
example, the direction of the low-frequency transverse mode rotates
together with the rotation when the torsion mode 502 is excited.
Thereby, a parametric oscillator is formed, since the natural
frequencies vary as a function of the rotation angle or thus as a
function of time. The transfer of energy between the different
states of the parametric oscillator brings about nonlinearities. In
that a rotational symmetry of high order is used, the formation of
the parametric oscillator can be prevented. Preferably, the support
elements are arranged in such a manner that there is no dependency
of the natural frequencies on the torsion angle.
[0187] By avoiding nonlinearities in the excitation of the torsion
mode of the support elements 101-1, 102-1, 101-2, 102-2, it can be
achieved that particularly large scanning angles of the light can
be achieved by the torsion mode 502.
[0188] The twisting of the support elements 101-1, 102-1, 101-2,
102-2 into one another along the central axis 220 and the twisting
of the support elements 101-1, 102-1, 101-2, 102-2 along their
longitudinal axes increase as the distances to the base 141
increase and they also increase as the torsion angles increase. For
example, if the torsion angle of the torsion mode 502 is greater
than the angular distance between the support elements 101-1,
102-1, 101-2, 102-2 (in the example of FIG. 18, 90.degree., due to
the four-fold rotational symmetry), there is a complete twisting
with longitudinal overlap of the support elements 101-1, 102-1,
101-2, 102-2 into one another. In general, the torsion angle of the
torsion mode 502 can thus be greater than 360.degree./n, where n
describes the order of the rotational symmetry. Thereby, the
twisting of the support elements 101-1, 102-1, 101-2, 102-2 into
one another is promoted. This parallel kinematics enables large
scanning angles with at the same time minor non-linear effects, in
particular a low space requirement.
[0189] FIG. 19 illustrates aspects with regard to a scanning module
100. In the example of FIG. 19, the scanning module 101 comprises a
single support element 101 with an optional balancing weight 1371.
Therefore, when the transverse mode 501 is excited, a tilting of
the mirror surface 151 occurs. This is represented in FIG. 20. In
FIG. 20, in particular the transverse mode 501 of lowest order is
represented. In other examples, it would also be possible to use a
transverse mode of higher order for the scanning of light 180,
wherein the deflection of the support element 101 at certain
positions along the length 211 of the support element 101 would
then be equal to zero (so-called node or bulge of the
deflection).
[0190] FIG. 21 illustrates aspects with regard to a scanning module
100. In the example of FIG. 21, the scanning module 101 comprises a
pair of support elements 101, 102. The support elements are
arranged in a plane (the plane of the drawing in FIG. 21). When the
transverse mode 502 is excited with deflection in this plane, no
tilting of the mirror surface 151 occurs. Therefore, the deflection
of the light 180 is not influenced by the excitation of the
transverse mode 502. This is represented in FIG. 22. Thereby, a
system-inherent stabilization with respect to vibrations can be
achieved. A particularly strong stabilization can be achieved, for
example, when more than two support elements which do not all lie
in the same plane are used. This would be the case, for example, of
the scanning module 100 according to the example of FIG. 17.
[0191] FIG. 23 illustrates aspects with regard to a scanning module
100. In the example of FIG. 23, the piezo actuators 310, 320 are
applied directly onto the support elements 101, 102, for example,
by vapor deposition processes. Thereby, it can be achieved that the
excitement of the degrees of freedom of motion 501, 502 does not
occur via the base 141; instead, it occurs directly in the region
of the support elements 101, 102. This can enable a particularly
efficient and space-saving excitation.
[0192] Alternatively or additionally to the excitation, the
corresponding piezoelectric layer can also be used to detect the
curvature of the support elements. Thereby, the deflection angle
901, 902 can be determined particularly precisely. For example,
multiple piezoelectric layers can be attached on different sides of
the support elements 101, 102 in order to detect different
directions of the curvature.
[0193] FIG. 24 is a flow chart of an example of a method for
producing a scanning module. For example, by means of the method
according to FIG. 24, the scanning module 100 according to
different examples described herein could be produced.
[0194] First, in step S001, on a wafer--for example, an Si wafer or
an SOI wafer--an etching mask is defined by means of lithography.
The wafer can have a thickness of 500 .mu.m, for example.
[0195] Then, in step S002, the wafer is etched. Here, the etching
can be carried out, for example, from the front side and/or from
the back side of the wafer. In this manner, the scanning module or
portions of the scanning module (etched structure) is/are obtained
in the form of a single-piece and free standing structure.
[0196] In step S002, the etching can occur from one or more sides
of the wafer. For example, first, the front-side etching could
occur, for example, with an SOI etching stop. Then, a back-side
etching could occur, for example, in order to define a recess in
the edge region of the base. Thereby, the edge region can obtain a
high form-induced resilience.
[0197] Optionally, subsequently multiple etched structures could be
connected to one another by gluing or anodic bonding (compare FIG.
17 and FIG. 25). Thereby, the scanning module--to the extent that
only parts are produced in step S002--can be completed. For
example, before the connection of etched structures for obtaining
the scanning module, a release of the etched structures to be
connected could occur for this purpose, the wafer could be cut or
sawed.
[0198] In step S003, the mirror surface is fastened to the scanning
module 100. The mirror surface could then enclose an angle with the
unetched wafer surface, for example, in the range of -60.degree. to
+60.degree., of optionally 45.degree. or 0.degree.. For example,
the mirror surface could enclose an angle with the unetched wafer
surface of 45.degree..+-.15.degree..
[0199] In a simple case, the fastening of the mirror surface could
comprise the deposition of aluminum or gold on a corresponding
surface of the scanning module 100 or of the interface element 142.
In other examples, for example, by means of an adhesive, a mirror
150 could be glued on the interface element 142. The mirror 150
could also be produced from a semiconductor material or else from
glass. Anodic bonding would also be possible in order to fasten the
mirror 150. Other examples of connection techniques comprise fusion
bonding, fusion or direct bonding, eutectic bonding,
thermocompression bonding, and adhesive bonding. Thus, in general,
the mirror 150 can be secured on the scanning module 100.
[0200] In step S004, in principle an optional step, the actuator
can be fastened on the scanning module 100. In a simple example,
this could comprise the deposition of piezoelectric material on the
support elements 101, 102 (compare FIG. 23). In other examples, it
would also be possible that, for example, piezo bending actuators
are fastened on the base 141.
[0201] FIG. 25 illustrates aspects with regard to the production of
a scanning module 100. In particular, FIG. 25 illustrates aspects
with regard to the connection of multiple etched structures 411,
412.
[0202] In FIG. 25, it is represented that two identically etched
structures 411, 412 are obtained by wafer processing. Each of the
etched structures forms in each case a corresponding base 141-1,
141-2, a corresponding interface element 142-1, 142-2, and support
elements 101-1, 102-1 and 101-2, 102-2.
[0203] In the example of FIG. 25, the base 141-1, the interface
element 142-1 and the support elements 101-1, 102-1 all have the
same thickness 1998, 1999 (in contrast to the scenario of FIG. 3).
In the example of FIG. 25, the base 141-2, the interface element
142-2 and the support elements 101-2, 102-2 all have the same
thickness 1998, 1999 (in contrast to the scenario of FIG. 3).
[0204] The two etched structures 411, 412 are connected to one
another, for example, by bonding, gluing, for example, with epoxy
adhesive or PMMA, etc. This is illustrated in FIG. 25 by the
dashed-line arrows.
[0205] In the scenario of FIG. 25, the etched structures are not
connected directly to one another. Instead, spacers 401, 402 are
used. Said spacers are not integrally formed with the etched
structures 411, 412. In detail, the base 141-1 of the etched
structure 411 is connected to the base 141-2 of the etched
structure 412 by a base spacer 401 arranged in between.
Furthermore, the interface element 142-1 of the etched structure
411 is connected via the interface spacer 402 to the interface
element 142-2 of the etched structure 412. For each spacer 401,
402, there are thus two connection surfaces on which, for example,
adhesive, etc., is applied--, which are each associated with one of
the two structures 411, 412.
[0206] Also represented in FIG. 25 is the plane of symmetry which,
by mirroring, brings the two structures 411, 412 together and thus
in particular reproduces the support elements 101-1, 102-2 into the
support elements 101-2, 102-2. By appropriate dimensioning of the
thickness of the spacers 401, 402, in turn an arrangement with
four-fold rotational symmetry can be achieved (compare FIG.
18).
[0207] The spacers 401, 402 can also be obtained by lithography
processing of a wafer. The spacers 401, 402 can also be produced
from silicon, for example. In the example of FIG. 25, the spacers
401, 402 are bulky parts with a low form-induced resilience. This
brings about a strong coupling of the two structures 411, 412
forming the scanning module 100.
[0208] By using the spacers 401, 402, in particular the distance
between the support elements 101-1, 102-1 and 101-2, 102-2 can be
adjusted in a flexible manner. In addition, it can be made possible
that the etched structures do not have to have any lateral
thickness variation--i.e., the bases 141-1, 141-2, the interface
elements 142-1, 142-2 and the support elements 101-1, 101-2, 102-1,
102-2 can all have the same thickness 1998, 1999. This enables a
particularly simple and less error-prone processing of the wafer.
In addition, the material is not stressed. For example, SOI wafers
can be dispensed with, since multiple etching stops are not
necessary. This can reduce the cost of the process.
[0209] The form-induced resilience of the edge region 146 is made
possible by the geometric form of the edge region 146: in the
example of FIG. 25, the edge region 146 of the bases 141-1, 141-2
is designed U-shaped. The central region 145 and the edge region
146 have the same thickness 1998. In order to promote a tilting of
the bases 141-1, 141-2 for the excitation of the torsion mode 502,
the edge regions 146 of the bases 141-1, 141-2 have an increased
form-induced resilience. In the example of FIG. 25, this is also
achieved by recesses which are arranged in the edge regions 146 at
a site facing the central regions 145 (highlighted in FIG. 25 by
the circle drawn with a dashed line). Corresponding details are
described in connection with FIG. 25.
[0210] FIG. 26 illustrates aspects with regard to the scanning
module 100. FIG. 26 is a cross-sectional view along line A-A' of
FIG. 25. FIG. 26 in particular illustrates aspects with regard to a
form-induced resilience of the edge regions 146 of the bases 141-1,
141-2.
[0211] In the example of FIG. 26, the bases 141-1, 142-2 comprise a
central region 145 and an edge region 146 (compare also FIG. 4).
Here, the edge regions 146 in each case have a recess 149 or
groove/notch/tapering. The recess 149 is arranged in each case
along an axis 148 which is arranged respectively perpendicularly to
the longitudinal axes 111, 112 of the support elements
(perpendicularly to the plane of the drawing of FIG. 26).
[0212] The recesses 149 are here arranged on a side of the bases
141-1, 141-2 facing the central region 145. The recesses 149 can be
arranged adjoining the central region 145. Thereby, a tilting of
the bases 141-1, 141-2 about the tilt axis can occur, the tilt axis
being arranged parallel to the longitudinal axes 111, 112 of the
support elements (perpendicular to the plane of the drawing of FIG.
26) (the tilting in FIG. 26 is represented by the dotted arrow).
Such a tilting can occur by piezo bending actuators which are
arranged at the edge regions 146--for example, at a distance from
the recesses 149 (compare also FIGS. 5A, 5B, 6A, 6B).
[0213] The recesses could be generated by back-side structuring of
a corresponding wafer, wherein the support elements can be
generated by front-side structuring. Thereby, during mechanical
ablation of wafer material, after the front-side structuring and
before the back-side structuring, in the area of the recess,
rupturing of the material or excessive stressing of the material
can be prevented from occurring.
[0214] Naturally, the features of the above-described embodiments
and aspects of the invention can be combined with one another. In
particular, the features can be used not only in the described
combinations, but also in other combinations or alone without
leaving the scope of the invention.
[0215] For example, various techniques have been above with regard
to the scanning module with a certain number of support elements.
However, the various techniques can also be used for scanning
modules having a different number of support elements.
[0216] While, for example, various techniques have been described
above with regard to a laser scanner, it would in general also be
possible to scan light other than laser light.
[0217] Various examples have been described with regard to a
temporal and spatial superposition of a transverse mode and a
torsion mode. In other examples, it would also be possible to
superpose other degrees of freedom of motion temporally and
spatially, for example, transverse modes of different orientation
and/or transverse modes of different order. In general, it is also
not necessary for a temporal and spatial superposition of different
degrees of freedom of motion to occur. For example, in different
scenarios, it would be possible that a degeneration between the
different modes is eliminated and an individual mode is excited in
a targeted manner.
[0218] For example, techniques of spatial and temporal
superposition for fiber-based scanners in the German patent
application DE 10 2016 010 448.1 have been discussed. The
corresponding disclosure content--for example, relating to
superposition figures and to the amplitude modulation of the
excitation--is included here by reference. The corresponding
techniques can also be used for single-piece MEMS scanners.
[0219] For example, techniques for the suppression of the tilting
of the mirror surface have been described with regard to the German
patent application DE 10 2016 013 227.2. The corresponding
disclosure content--for example, relating to the rotationally
symmetrical arrangement of multiple fibers--is included here by
reference. The corresponding techniques can also be used for MEMS
scanners.
[0220] Moreover, the above described examples have been described
in connection with a piezoelectric drive. However, the techniques
described herein can also be used with other drive forms, for
example, a magnetic drive or an electrostatic drive.
* * * * *